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Modern crocodiles and alligators came from different environments – ScienceDaily

A new study questions the notion that today's crocodiles and alligators have a simple evolutionary past.

Previous research has pointed to crocodiles and alligators who started with a land-based ancestor about 200 million years ago and then moved to fresh water, they become semi-aquatic ambush animals they are today.

But a new analysis published online today in the journal Scientific Reports gives a different story. Modern crocodiles and alligators came from a number of environments that began in the early Jurassic period, and various species occupied a wide variety of ecosystems over time, including land, estuaries, freshwater and marine.

As the University of Iowa co-author Christopher Brochu researches and studies, "Crocodiles do not live fossils. Transitions between land, sea and freshwater were more frequent than we thought, and the transitions were not always land-to-freshwater or freshwater at sea."

Brochu and colleagues from Stony Brook University linked crocodiles and alligator fathers by analyzing a large pedigree showing the evolutionary history of living and extinct crocodylomorphs (modern crocodiles and alligators and their extinct relatives). The team could then predict the ancestral habitat of several divergence points on the evolutionary tree.

This suggests a complex evolutionary story not only of habitat but of form. Those who live on the sea had paddles instead of limbs, and they on land often had hoof-like claws and long legs. These did not all evolve from ancestors resembling modern crocodiles that have long assumed.

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Materials from University of Iowa . Note: Content can be edited for style and length.